1. Technical Field
The presently disclosed subject matter relates to a metal multi-layered film structure and method of forming the same, and more particularly to a metal multi-layered film structure formed on a resin substrate by sputtering and its related method of manufacturing. It also relates to an extension reflector for vehicles having the above-described metal multi-layered film structure.
2. Description of the Related Art
A conventional structure of a vehicular lamp is shown in FIG. 5. A lens cover 50 and a lamp body 51 form a lamp chamber 52, which houses a light source bulb 53 and a reflector 54 located around the light source bulb 53. The light L emitted from the light source bulb 53 toward the reflector 54 is reflected from the reflector 54 and released through the lens cover 50 to the front of the lamp.
When the above-configured vehicular lamp is observed from the front while the light source is turned off in the daytime, the lamp body 51 located behind a gap 55 formed between the reflector 54 and the lamp body 51 can be seen through the lens cover 50 and through the gap. This structure deteriorates the appearance of the lamp.
In particular, there is a vehicular lamp that includes a plurality of lamp bodies each including a separate light source bulb and reflector in combination within the lamp chamber. In such a case, the lamp body portion located behind the lamp reflectors can be seen through the gap formed between the reflectors and the lamp body portion, and additionally through the gap formed between adjacent reflectors. This structure further deteriorates the appearance of the lamp.
To prevent occurrence of such the problem, an extension reflector 56 is disposed within the lamp chamber 52 in a region relatively less related to the optical system. The extension reflector 56 covers the portion of the lamp body 51 that is located behind the reflector and is otherwise viewable, in order to enhance the appearance of the lamp. In addition, an observer can visually identify the extension reflector 56 because it receives extraneous light, thereby producing a refined appearance design for the lamp.
An enlarged view of an example of the general structure of the extension reflector 56 is shown in FIG. 5. The reflector 56 can include a resin substrate 60, on which an under coat 61 composed of an acrylic-based resin or the like for smoothing the rough surface of the resin substrate is applied and dried/cured. On the under coat, a coloring coat 62 for giving the lamp an upgraded image and for refining and chromatically differentiating the appearance and design of the lamp is applied and dried/cured. Further, on the color coat, a topcoat 63 for protection is applied and dried/cured to complete a multi-layered film structure.
Another example of forming a multi-layered film on a resin substrate is shown in FIG. 6. The film can include an ABS resin 70, on which a polyester urethane-based base coat 71 is applied and dried. On the base coat, a metal multi-layered film 72 is formed by forming SiO2 (ceramic) films and Cu films alternately or simultaneously by sputtering. Further, an acrylic urethane-based topcoat 73 is applied on the metal multi-layered film and dried to complete a brilliant multi-layered film according to this method (see Japanese Patent Document 1: JP-A 62-89859, for example).
The multi-layered film structure shown in the enlarged view of FIG. 5 can include at least three coating steps for the under coat, the coloring coat and the protection film coat (topcoat). In addition, in the method shown in FIG. 5, time should be reserved for drying/curing after coating in each of the coating steps. Therefore, time and effort go into forming the multi-layered film which, in some circumstances, results in poor production efficiency when time and/or effort is/are deficient.
The formation of films through coating causes the multi-layered film structure to have a total film thickness of about 20 μm or more, which correspondingly increases the material expense and elevates the production cost.
The repetition of a series of coating steps including coating and drying/curing increases the degree of attachment of dirt and debris to the coated surface during the method and may lower the production yield.
An organic solvent may be used as a solvent for coating during the above-described manufacturing processes. However, it is desirable to reduce or hold back the use of organic solvents, not only from the viewpoint of environmental concerns but also from the viewpoint of protecting the health of workers.
On the other hand, as for the multi-layered film structure shown in FIG. 6, the base coat and the topcoat are formed by coating, and the metal multi-layered film composed of SiO2 films and Cu films are formed by sputtering. Therefore, different types of facilities are often used in the forming of the multi-layered film, such as a coating facility and a sputtering facility, which increase the cost related to the production facilities. In addition, handling procedures for transportation between the different types of facilities lowers the production efficiency and yield, becoming a factor that also elevates the production cost.
The SiO2 films and Cu films described in Japanese Patent Document No. JP-A 62-89859 referenced above both have a single-layered film thickness of around 50 nm, which is thicker as the film thickness formed by sputtering, and extends the time for film formation, correspondingly. Therefore, an increase in the number of film layer formations results in an elongated time for film formations and increasingly lowers the production efficiency.